Method of changing dies for a press machine

ABSTRACT

A method of changing dies for a press machine of the type including two or more slides (3a, 4a) arranged in a side-by-side relationship of which lower dead point in terms of a crank angle is different from one another, wherein a resilient member (10) is interposed between upper die halves (7a, 8a) and lower die halves (7b, 8b) for the respective slides (3a, 4a) and movement of the respective slides (3a, 4a) is simultaneously interrupted at a crank angle in the proximity of an intermediate angle between the plural lower dead points so that clamping of upper die halves (7a, 8a) to and unclamping of the upper die halves (7a, 8a) from the respective slides are achieved during the interruption of movement of the respective slides, whereby mounting of dies on or dismounting of the same from presses is simultaneously achieved for the respective slides (3a, 4a).

TECHNICAL FIELD

The present invention relates to a method of changing dies for a pressmachine such as a transfer press or the like having two or more slidesarranged in a side-by-side relationship of which lower dead point interms of a crank angle is different from each other.

BACKGROUND ART

As shown in FIG. 10, a hitherto known transfer press employable mainlyfor deep drawing operations is provided with a link driven type slide badapted to be driven by a link mechanism on the upstream side as seen inthe direction of transference of works (as represented by an arrow marka) and an eccentric gear driven type slide (hereinafter referred to asan eccentric driven type slide) d adapted to be driven by an eccentricportion on the main shaft via a connecting rod on the downstream side.

With such conventional transfer press, a crank angle representative ofthe lower dead point of the link driven type slide b for deep drawingoperation on the upstream side is deviated from a crank anglerepresentative of the lower dead point of the eccentric driven typeslide d by an angle in the range of 10° to 20°. For the reason, when theone slide has reached the lower dead point, the other slide has still acertain amount of gap between the upper die half and the lower die half.

In view of this fact, conventional die changing is achieved for twoslides in such a manner that one of the dies is separately unclampedfrom the corresponding slide at the different time when the latter islowered to its lower dead point. This leads to drawbacks that a longtime is required for die changing and die changing operations areperformed at a reduced efficiency.

The present invention has been made with the foregoing background inmind and its object resides in providing a method of changing dies for apress machine of the type including two or more slides of which lowerdead point in terms of a crank angle is different from each other whichassures that the dies on the slides can simultaneously be exchanged withanother ones and a time required for die changing can be reducedsubstantially.

DISCLOSURE OF INVENTION

To accomplish the above object, the present invention provides a methodof changing dies for a press machine of the type including two or moreslides of which lower dead point in terms of a crank angle is differentfrom each other, wherein elastic means is interposed between an upperdie half and a lower die half for the respective slides and movement ofthe respective slides is simultaneously interrupted at a crank angle inthe proximity of an intermediate angle between the plural lower deadpoints so that clamping of the upper die half to or unclamping of thesame from the respective slides is achieved during the interruption ofmovement of the respective slides.

According to the present invention, when the respective slides are heldimmovable, the lower surfaces of the upper die halves come in contactwith the upper surfaces of the lower die halves with elastic meansinterposed therebetween and the respective slides remain at the sameheight. Thus, when the respective upper die halves are unclamped fromthe respective slides as long as the aforementioned state is maintained,the upper die halves are placed on the lower die halves via the elasticmeans without an occurrence of falling-down of the upper die halves onthe floor. Similarly, upper die halves on plural slides cansimultaneously be unclamped from the latter, e.g., by displacingrespective bolsters outside of the press line. Things are the same witha case where the upper die halves are clamped to the respective slides.Namely, when the respective slides reach the vicinity of theintermediate angle, their movement is interrupted so that the upper diehalves can simultaneously be clamped to them.

Consequently, according to the present invention, die changing (dieunclamping/die clamping) can simultaneously be achieved with therespective slides. This assures that a time required for die changingcan substantially be reduced and a transfer press can be operated at animproved efficiency in comparison with the conventional die changingwhich has been executed separately for respective slides. Further, sincethere is no need of providing a control circuit required for diechanging separately for respective presses, electric circuits can besimplified and they can be produced at an inexpensive cost.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view illustrating a transfer press for which a methodin accordance with an embodiment of the present invention is employed,

FIG. 2 is a plane view of the transfer press in FIG. 2,

FIG. 3 is a timing diagram for a link driven type slide,

FIG. 4 is a timing diagram for an eccentric driven type slide,

FIG. 5 is a timing diagram for both the link driven type slide and theeccentric driven type slide,

FIG. 6 is an enlarged front view of an elastic stopper usable for thetransfer press in accordance with the embodiment of the presentinvention shown in FIGS. 1 and 2,

FIG. 7 is a partial view illustrating both presses at the time ofclamping/unclamping of dies,

FIG. 8 is a block diagram illustrating by way of example the structureof a control system,

FIG. 9 is a step diagram illustrating a series of steps to be performedat the time of die changing, and

FIG. 10 is a front view illustrating a transfer press for which aconventional method is employed.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention will be described in detail hereinafter withreference to the accompanying drawings which illustrate a preferredembodiment thereof.

FIG. 1 is a front view illustrating a transfer press for which themethod in accordance with an embodiment of the present invention isemployed and FIG. 2 is a plan view of the transfer press in FIG. 1.

In FIGS. 1 and 2, reference numeral 1 designate a housing for the threecolumn type transfer press including three sets of uprights 1a, 1b and1c. The transfer press comprises a link press 3 disposed on the upstreamside as seen in the direction a of transference of works (or workpieces) 2 to include a link driven type slide 3a and an eccentric press4 disposed on the downstream side to include an eccentric gear driventype slide 4a (hereinafter referred to as an eccentric driven typeslide). Both the link driven type slide 3a and the eccentric driven typeslide 4a are driven by a single main motor (not shown).

The link press 3 is such that the slide 3a is driven in the verticaldirection via a link mechanism so that works 2 are subjected to pressforming between three upper die halves 7a clamped to the slide 3a andthree lower die halves 7b clamped to a moving bolster 3b. With this linkdriven type slide 3a, a relationship as represented by a curve A in FIG.3 is established between a crank angle and a feed stroke. In theillustrated case, the slide 3a has a lower dead point represented by acrank angle of 192°. Usually, the link driven type slide 3a has a crankangle representative of the lower dead point in the range of 190° to200°. Incidentally, in FIG. 3 curves B, C and D show operations oftransfer bars 6.

As is well known, the eccentric press 4 is such that the slide 4a isdriven in the vertical direction via a slide driving mechanism (notshown) comprising an eccentric portion arranged around the main shaftand a connecting rod so that works 2 are subjected to press formingbetween three upper die halves 8a clamped to the slide 4a and threelower die halves 8b clamped to a moving bolster 4b. With this eccentricdriven type slide 4a, a relationship as represented by a curve A. inFIG. 4 is established between a crank angle and a stroke. This eccentricdriven type slide 4a has a lower dead point represented by a crank angleof 180°. Incidentally, in FIG. 4 curves B, C and D likewise showoperations of transfer bars 6.

As is apparent from FIG. 5, the transfer press in accordance with thisembodiment has a deviation of about 12° between the lower dead pointcrank angle for the slide 3a of the link press 3 and the lower deadpoint crank angle for the slide 4a of the eccentric press 4.

Referring to FIGS. 1 and 2 again, works 2 which have been introducedinto the housing 1 of the transfer press by a destacker 5 aresuccessively transferred to respective work stations in the eccentricpress 4 by the transfer bars 6 adapted to be displacedthree-dimensionally. In the illustrated case, each of the transfer bars6 has five sections 6₁, 6₂, 6₃, 6₄ and 6₅ divided by bar connectors 6a,6b, 6c and 6d on one side. To assure that the works 2 are clampedbetween both the upper and lower die halves, the respective transferbars 6 have a plurality of fingers 9 attached thereto.

The moving bolsters 3b and 4b are intended to move on rails 11 in thetransverse direction relative to the direction of transference of theworks 2 in order to assure that die changing is achieved easily andquickly. In the illustrated case, the transfer press has two movingbolsters for the link press and two bolsters for the eccentric press(i.e., four moving bolsters in total). This is intended to provide sucha convenience that with respect to both link press and eccentric pressone of the moving bolsters remains in a waiting state with a die andtransfer bars to be used for next press work placed thereon while theother one is put in practical use. Each of the four moving bolsters 3b,3b', 4b and 4b'is provided with a plurality of bar holders 12 on whichthe transfer bars 6 are placed when they are expanded to their maximumwidth.

In addition, each of the moving bolsters 3b, 3b', 4b and 4b'is providedwith work holders 13 on one side wall thereof so as to provide betweenthe link press 3 and the eccentric press 4 an idle station on which thework is temporarily held. This means that in this transfer press thetransfer bars 6 have a feed stroke which is set to 1/4 of a centerdistance L between the link press 3 and the eccentric press 4, i.e.,L/4. To prevent the work holders 13 constituting an idle station fromcolliding with the upright 1b during movement of the moving bolster,they are turnable by 90 degrees.

To provide a safety for press operations, a plurality of safety fences14 are arranged outside of the transfer press in such a manner that theyare automatically lifted up when the moving bolsters move.

With such construction of the transfer press, each of the lower diehalves 7b and 8b is equipped with four elastic stoppers 15 made of,e.g., polyurethane resin. The elastic stoppers 15 serve not only asshock absorbers between upper and lower die halves during pressoperation but also as interpositions between upper and lower die halvesduring die changing.

Specifically, the elastic stopper 15 assumes a state as represented bysolid lines in FIG. 6 under no load but it has a state as represented bydotted lines in the drawing in the presence of its elasticity when itreceives a certain intensity of press force. The transfer press inaccordance with the present invention is intended to perform a step ofdie changing by utilizing the aforementioned nature of the elasticstoppers 15. In detail, while the step of die exchanging is performed,the slides 3a and 4a of the link press 3 and the eccentric press 4 aresimultaneously stopped when an intermediate angle between the lower deadpoint crank angle of the link driven type slide 3a (192° in theillustrated case) and the lower dead point crank angle of the eccentricdriven type slide 4a (180° in the illustrated case), i.e., theintermediate angle of 186° in the illustrated case is reached. At thismoment, the upper die halves 7a and 8a for both the presses 7a and 8acan simultaneously be unclamped from the slides 3a and 4a. As shown inFIG. 7, when the intermediate angle of 186° is reached, the slide 3a ofthe link press 3 is moving downwardly toward the lower dead point whilethe slide 4a of the eccentric press 4 is moving upwardly away from thelower dead point. At this moment, an appreciable amount of gapcorresponding to a crank angle of 6° is existent between both the upperand lower die halves of the presses 3 and 4. In practice, the elasticstopper 15 is so designed that the gap is less than the height h of theelastic stopper 15 under no load (see FIG. 6). Thus, there is no fearthat the upper die halves 7a and 8a fall down on the floor when they areunclamped from their slides 3a and 4a, as long as the aforementionedstate is maintained. Namely, they are immovably held on the lower diehalves 7b and 8b via the elastic stoppers 15 interposed therebetween.Then, die changing can simultaneously be achieved for the link press 3and the eccentric press 4 by raising up the slides 3a and 4a and thenexchanging the working bolsters with the waiting bolsters.

FIG. 8 shows by way of example the structure of a control system for thetransfer press. The control system comprises a bolster driving unit 20for controlling the movement of moving bolsters 3b, 3b', 4b and 4b'andthe driving of respective components, a transfer bar driving unit 30 forcontrolling the three-dimensional movement of transfer bars 6 and thedriving of respective components associated therewith, a press drivingunit 40 for controlling the raising/lowering of slides of the link press3 and the eccentric press 4 and the driving of respective components, asafety fence raising/lowering unit 50 for raising and lowering thesafety fences 14 and a press controller 60 for executing total controlfor the aforementioned units.

Next, operations during the die exchanging as mentioned above will bedescribed in detail below with reference to FIG. 9 which shows a stepdiagram.

First, a die change button (not shown) is turned on by an operator (step1). When completion of the step 1 is confirmed, the press controller 60gives a command the transfer bar driving unit 30 to lock feed levers(not shown) so as not to allow the transfer bars 6 to be displaced inthe direction a of transference of works as the crank shaft is rotated(step 2). At this moment, the press controller 60 executes a forciblebar unclamping operation for expanding the width between the transferbars 6 on both sides to the maximum one (step 3). In addition, at thesame time, lowering of the die cushions (not shown) is initiated,whereby the moving bolsters 3b and 4b are ready to move (step 9).

Next, the press controller 60 gives a command to the bolster drivingunits 20 and the transfer bar driving unit 30 at the time when step 3 isterminated so that the transfer bars 6 are lowered so as to allow themto be placed on the bar holders 12 attached to the moving bolsters 3band 4b while their width is expanded to the maximum one (step 4). Atthis moment, the work holders 13 attached to the bolsters 3b and 4b asidle stations are turned by an angle of 90° until the former arereceived in the latter (step 5). Then, the idle fingers 9(representative of fingers fitted to the transfer bars 6₃) adapted toclamp a

work on the idle station are displaced to predetermined positions on thebolster 3b or 4b (step 6). Displacing means (not shown) is provided forthe purpose of displacing the idle fingers 9 so that retraction of theidle fingers 9 permits them to be replaced with new ones incorrespondence 5 to a die to be next used.

Thereafter, the press controller 60 gives a command to the transfer bardriving units 30 at the time steps 4, 5 and 6 are terminated so that thejoint connectors 6a, 6b, 6c and 6d for the transfer bars 6 are releasedso as to allow the transfer bars 6 to be divided into five sections 6₁to 6₅ (steps 7 and 8).

In addition, the press controller 60 gives a command the press drivingunit 40 at time steps 7 and 8 are initiated so that the link press 3 andthe eccentric press 4 start to lower their slides 3a and 4a (step 10).At this moment, the slide 3a of the link press 3 and the slide 4a of theeccentric press 4 perform their lowering movement along curves A and A'in FIG. 5.

As both the slides 3a and 4a are lowered, first the slide 4a of theeccentric press 4 reaches the lower dead point (represented by a crankangle of 180°) and then it starts to be raised up. Thereafter, when thecrank angle reaches 186°, the slides 3a and 4a of both the presses 3 and4 have the same height, as shown in FIG. 7. Namely, when the crank anglehas reached 186°, the slide 3a is moving downwardly and the slide 4a ismoving upwardly.

When the press controller 60 detects that the crank angle has reached186°, it gives a command the press driving unit 40 so thatupward/downward movement of both the slides 3a and 4a is interrupted andupper die halves 7a and 8a are simultaneously unclamped from the slides3a and 4a (step 11). At this moment, an appreciable amount of gapcorresponding to a crank angle of 6° exists between the upper and lowerdie halves on the presses 3 and 4, as mentioned above. To adapt to thegap, the elastic stoppers 15 are so designed that the gap is less thanthe height h of the elastic stopper 15 under no load (see FIG. 6). Aslong as the foregoing state is maintained, there does not arise amalfunction of the upper die halves 7a and 8a falling down on the floorwhen they are unclamped from the slides 3a and 4a. Rather, they areimmovably held on the lower die halves 7b and 8b with the elasticstoppers 15 interposed therebetween.

On completion of the unclamping operations for the upper die halves 7aand 8a, the press controller 60 restart to drive the slides 3a and 4a.Namely, the slide 3a of the link press 3 is lowered further and it isthen raised up after it reaches the lower dead point (representative ofa crank angle of 192°). In the meantime, the slide 4a of the eccentricpress 4 is raised up.

Thereafter, on completion of the dividing operations for the transferbars 6 at the step 8, the press controller 60 outputs a command to thebolster driving unit 20 so as to allow MB clampers (not shown) withwhich the moving bolsters 3b and 4b are fixed to their beds to beunclamped (step 13). Then, the MB clampers are raised up (step 14),whereby the moving bolsters 3b and 4b are ready to move on the rails 11.At the same time, the press controller 60 gives a command to the safetyfence raising/lowering unit 50 so that all the safety fences 14 areraised up (step 17).

Next, the press controller 60 outputs a command to the bolster drivingunit 20 so as to allow the moving bolsters 3b and 4b to move in thedirection of arrow marks e in FIG. 2 until they are simultaneouslydisplaced to their waiting positions as represented by dotted lines inFIG. 2. It should be noted that in addition to the upper and lower diehalves, the transfer bars 62 and 64 and the idle fingers are mounted onthe moving bolsters 3b and 4b.

On the other hand, other moving bolsters 3b'and 4b'are previouslyprovided for the presses 3 and 4, and in addition to die halves 7a',7b', 8a' and 8b' to be next used, transfer bars 6₂ ' and 6₄ ' havingfingers 9 attached thereto in correspondence to these die halves andidle fingers are previously mounted on the bolsters 3b' and 4b'. As themoving bolsters 3b and 4b are displaced away from their workingpositions, the moving bolsters 3b' and 4b' are caused to move into thepress housing 1 (step 16).

Thereafter, reverse operations to those in the steps 1 to 15 areperformed at steps 17 to 31 so that lowering of the safety fences 14,clamping of the upper die halves 7a' and 8a' to the slides 3a and 4a andreturning of the transfer bars to their operative state are achieved,whereby the intended die changing is terminated completely.

Incidentally, at the steps 20 to 22 movement of both the slides 3a and4a is interrupted when the crank angle reaches an intermediate angle of186° between the lower dead point crank angles of both the slides 3a and4a in the same manner as at the aforementioned steps 10 to 12. At thistime, upper die halves 7a' and 8a' can simultaneously be clamped to boththe slides 3a and 4a.

In this manner, according to the foregoing embodiment, when die changingis executed in a transfer press of the type including a link press 3 andan eccentric press 4 of which slide has a different lower dead pointrepresented by a crank angle from each other, movement of the slides 3aand 4a of both the presses 3 and 4 is simultaneously interrupted so asto allow upper die halves to be unclamped from the slides and theunclamped upper die halves are elastically supported on elastic stopperson lower die halves. With the above construction, there does not arise amalfunction the upper die halves falling down on the floor. Instead,they are immovably held on the lower die halves. Thereafter, bydisplacing moving bolsters away from their working positions, theworking dies for both the presses can be removed simultaneously.

Next, die mounting is achieved in the following manner. New dies, eachincluding an upper die half to be next used and a lower die half to benext used while the former is placed on the latter with elastic stoppersinterposed therebetween, are clamped to the moving bolsters. Then,movement of the slides 3a and 4a of both the presses 3 and 4 issimultaneously interrupted at an intermediate angle between the lowerdead point crank angles of both the slides in the same manner asmentioned above. While the foregoing state is maintained, upper diehalves are clamped to both the slides. In this manner, the new dies forboth the presses can simultaneously be mounted on the latter.

Thus, the method of the present invention makes it possible toremarkably reduce a time required for die changing in comparison withthe conventional method of die changing. This permits the transfer pressto be operated at an improved operational efficiency. Further, sincethere is no need of arranging a separate control circuit for diechanging of the respective presses, the electrical circuits can besimplified and thereby they can be produced at a reduced cost.

It should be noted that the present invention should not be limited onlyto the foregoing embodiment but various changes or modification maysuitably be made with the present invention. In the foregoingembodiment, the crank angle employed at the time of unclamping/clampingof the dies is set to an intermediate angle between the lower dead pointcrank angles of both the slides. Strictly speaking, the intermediateangle should not necessarily be selected in that way. Alternatively, anangle in the vicinity of the intermediate angle can be employed with thesame advantageous effects as in the foregoing embodiment. Namely, thecrank angle at the time of unclamping/clamping may be determined independence on the height h of the elastic stoppers under no load, theirelastic properties and so forth.

The foregoing embodiment has been described above with respect to atransfer press of the type including two slides. Alternatively, thepresent invention may be applied to a transfer press including three ormore slides of which lower dead point in terms of a crank angle isdifferent from each other.

Further, in the foregoing embodiment, the elastic stoppers 15 are fittedto the lower die half. Alternatively, they may be fitted to the upperdie half.

Moreover, in the foregoing embodiment, a transfer die feeder is employedas work transferring means. Alternatively, the present invention may beapplied to a press machine including a progressive die or the like forwhich a work is transferred by transferring means other than a transferfeeder.

INDUSTRIAL APPLICABILITY

The present invention is useful for changing dies for a press machinesuch as a transfer press or the like including two or more slides ofwhich lower dead point in terms of a crank angle is different from eachother.

I claim;
 1. A method of changing dies in a press machine having aplurality of dies each having an upper die half respectively supportedby corresponding slides and a lower die half, said slides arranged withtheir respective lower dead points different from each other based on acommon crank angle, which comprises:interposing elastic means betweensaid upper die half and said lower die half of said plurality of dies,and interrupting movement of said corresponding slides at a crank anglein proximity of an intermediate angle between said respective lower deadpoints for clamping of said upper die halves to or unclamping of saidupper die halves from their corresponding slides during saidinterrupting of movement of said corresponding slides.
 2. The method asclaimed in claim 1, wherein said interposing step includes fitting saidelastic means to an upper surface of said lower die half.
 3. The methodas claimed in claim 1, wherein said interposing step includes fittingsaid elastic means to a lower surface of said upper die half.
 4. Themethod as claimed in claim 1, wherein said elastic means comprises aplurality of elastic members.
 5. The method as claimed in claim 1,wherein said press machine comprises a transfer press including transferbars for successively transferring a number of work pieces therethrough.6. A method for changing dies in a press machine having a plurality offirst dies each having a first upper die half respectively mounted oncorresponding slides and a first lower die half respectively mounted ona corresponding first moving bolsters, said slides arranged with theirrespective lower dead points different from each other based on a commoncrank angle, which comprises:interposing elastic means between saidfirst upper die halves and said first lower die halves of said pluralityof first dies, and unclamping said first upper die halves from saidslides, repositioning said slides, retracting said first moving bolstersfrom said press machine to predetermined positions, positioning secondmoving bolsters within said press machine, said second moving bolsterscarrying second dies each having a second lower die half mounted thereonand a second upper die half resting of said second lower die half,positioning said slides at said crank angle in proximity of anintermediate angle between said respective lower dead points, andclamping said second upper die halves to said slides.
 7. The method asclaimed in claim 6, wherein said interposing step includes fitting saidelastic means to an upper surface of first said lower die half.
 8. Themethod as claimed in claim 6, wherein said interposing step includesfitting said elastic means to a lower surface of said first upper diehalf.
 9. The method as claimed in claim 6, wherein said elastic meanscomprises a plurality of elastic members.
 10. A method of changing diesfor a press machine having a plurality of first dies each having a firstupper die half respectively mounted on corresponding slides and a firstlower die half respectively mounted on first moving bolsters, and aplurality of first transfer bars for successively feeding a number ofwork pieces to said press machine, said slides arranged with theirrespective lower dead points different from each other based on a commoncrank angle, which comprises:interposing elastic means between saidfirst upper die halves and said first lower die halves of said pluralityof first dies; lowering and placing said first transfer bars on saidfirst moving bolsters; dividing each of said first transfer bars intoplural slide units, positioning said slides at a crank angle inproximity of an intermediate angle between said respective lower deadpoints, unclamping said first upper die halves from said slides,repositioning said slides, retracting said first moving bolsters fromsaid press machine to predetermined positions, introducing second movingbolsters within said press machine, said second moving bolster carryingsecond dies each having a second lower die half mounted thereon and asecond upper die half resting on said second lower die half,repositioning said slides at said crank angle in proximity of anintermediate angle between said respective lower dead points, clampingsaid second upper die halves to said slides, repositioning said slides,connecting plural divided slide units of second transfer bars to eachother on said second moving bolsters, and raising said second transferbars upwardly away from said second moving bolsters.
 11. The method asclaimed in claim 10, wherein interposing step includes fitting saidelastic means to a upper surface of said first lower die half.
 12. Themethod as claimed in claim 10, wherein interposing step includes fittingsaid elastic means to a lower surface of said first upper die half. 13.The method as claimed in claim 10, wherein said elastic means comprisesa plurality of elastic members.